Lock-stitch sewing machine



May 20, 1941. J, D, KARLE Loox-STITCH SEWING MACHINE Filed April 8, 1939 3 Sheets-Sheet 1 f 30? www J. D. KARLE 2,242,955

LOCKSTITCH SEWING MACHINE Filed April 8, 1939 3 Sheets-Sheet 2 @lohn D. Karl'e May 20, 1941. J, D KARLE 2,242,955

LOCK-STITCH. SEWING MACHINE Filed Apgn 8, 1959 s sheets-sheet s lf3-9T John 0. Karla ivgwlww Patented May 20, 1941 UNITED STATES PATENT OFFICE Singer Manufacturing Company,

Elizabeth,

N. J., a corporation of New Jersey Application April 8,'1939, Serial No. 266,786

(Cl. liz- 181) 14 Claims.

This invention relates to lock-stitch sewing machines more particularly of the type having a reciprocatory eye-pointed needle and a complemental looptaker with which is associated a bobbin of under thread about which loops of the needle-thread are cast by the loop-taker in the forlation of stitches.

The problem of supporting the bobbin for the free casting of the needle-loops thereabout, in a machine of the type referred to, has received much attention in the development of the lockstitch sewing machine art and, at the present time, the conventional practice is Ato dispose the bobbin in a non-rotary bobbin-case having a peripheral bearing-rib received in an internal groove in the rim of a cup-shaped rotary looptaking hook. During long' runs at high speeds, the friction between the stationary and moving bearing surfaces of the bobbin-case and hook overheats the parts, making them too hot to handle in bobbin replenishment and causing premature and destructive wear. Various attempts have been made to reduce or eliminate this objectionable friction but no solution has been pro posed which has the requisite simplicity, effec- .tiveness and freedom from drawbacks to gain recognition over the clean running conventional hook and bobbin-case disclosed in the U. S. Patent to C. A. Kessler, No. 1,995,278 of Mar. 19, 1935.

The present invention has for an object to provide simple and practical means to materially reduce raceway friction and wear in a sewing machine rotary hook more particularly of the type shown in said Kessler patent, without sacriiice of the clean running, high-speed sewing characteristics of such hook.

Further objects of the invention will in part be obviousand in part hereinafter appear.

The invention will be understood from the following detailed description taken in connection with the accompanying drawings of which Fig. 1 is a side elevation, partly in section, of a sewing machine embodying the invention in a preferred form. Figs. 2 and 3 are sectional views, on a larger scale, of the hook and bobbin-case-supporting mechanism of Fig. 1, at two different instants of a stitch-forming cycle. Fig. 4 is a bottom plan view of the bobbin-case-supporting rodreciprocating mechanism. Fig. 5 is a perspective View of the rotary hook element. of the present improvement. Fig. 6 is a perspective view of the bobbin-case element. Fig. 'I is a longitudinal vertical sectional view of a modified form of the invention. Fig. 8 is a similar view with the bobbincase supporting means of Fig. 7 withdrawn for passage of the needle-thread-loop. Fig. 9 is a left end elevation of the device shown in Fig. '1, and Fig. 10 is a perspective view of a cam element included in the form of the invention shown in Figs. 7, 8 and 9.

Referring first to the preferred embodiment of the invention illustrated in Figs. 1 to 6, both inclusive, I represents the bed of a sewing machine from which rises the conventional standard 2 of the overhanging bracket-arm 3 terminating in the head I. The main shaft 5 carrying the balance wheel 6 and power-receiving beltpulley l is journaled within the overhanging arm 3 and has the conventional crank 8 and link 9 connections for reciprocating the needle-bar I0 carrying the eye-pointed needle II. The shaft 5 also drives the conventional link take-up I2 which handles the needle-thread in the usual manner. Geared to and driven by the top shaft 5, in one-to-one relation, is the vertical shaft I3 to the lower end of which is secured the crankhead Il and bevel gear I5; the crank-head carrying the crank-pin I6 and slide-block 34.

Journaled in bearing bushings Il, I8, below the bed I, is the tubular hook-shaft I9 to the left end of which is secured the cup-shaped rotary hook-body 20 having the usual internal peripheral bearing gro'ove 2| for the peripheral bearing rib 22 of the bobbin-case 23 which is conventional in all respects with the exception of the hole 24 formed in its rear face coaxial with the central arbor pin 25. A slightly increased working clearance over conventional practice is preferably allowed between the juxtaposed bearing surfaces of the rib 22 and groove 2i. Except for the hole 2l, which is coaxial with the peripheral bearing rib 22, and the slightly increased raceway bearing clearance, the hook 20 and bobbin-case 23 are preferably constructed substantially in wccordance with the disclosure of the said Kessler patent; the thread-case 23 being restrained against rotation by the usual rotation-restraining bar 26 having a` tongue 2l which loosely enters a notch 28 in the front face of the bobbin-case. The bobbin-case 23 also has the usual gap in its bearing rib 22 affording the stationary loopcatching shoulder 29 which detains one limb of the needle-thread loop after it is seized from the needle by the beak 20 of the rotary hook, in the operation of casting the loop about the bobbin-case.

The non-rotary bobbin-case 23 is, in accordance with the present invention, supported truly centrally within the field of action of thehook 20 by an endwise reciprocatory rod 30 which extends within and lengthwise of the tubular hook-shaft I9 fitted at its opposite ends with bearing bushings 3I through which the rod 30 extends. At its right-hand end, the rod 30 has xed to it a rectangular yoke 32 having a slot 33 for the crank slide-block 34. A nut 35 and washer 36 cooperate with the flat bottomed face of the crank-head I4 to confine the yoke 32 and rod 30 against rotation with the shaft I9.

The hook-shaft I9 has xed to its rearward end, a bevel gear 31 of half the pitch-diameter of the bevel gear I with which it meshes and is driven`at twice the speed of the top-shaft 5.

` When the rod 30 "is in the hole 24, it sustains the weight of the bobbin-case and relieves the peripheral bearing surfaces of friction from this revolution for two revolutions of the hook-shaft.

cause. The working position of the free end of the rod and the radius of the crank I6 are so contrived that the freeend of the rod 30 is in the hole 24 as long as possible and is withdrawn from the hole but a small fraction of the time of one stitch-forming cycle, as shown in Fig. 3, for the passage lof the inner limb 38 of the cast needle-thread-loop. For example, the radius of the crank I6 may be if inch giving a stroke of' rotation of the hook-shaft I9, which is 1/3 of aL stitch-forming cycle.

The free end of the rod 36 or the mouth of the hole 24, or both. should preferably have their corners broken or slightly beveled, to insure pick up of the bobbin-case by the rod 36 when the v machine is being turned over slowly or atrmoderate speeds. At high speeds it is believed the bobbln-case practically oats in space during the exceedingly short time intervals that the rod 30 is out of the hole 24.

In theembodiment of the invention shown in Figs. 7, 8, 9 and 10, two opposed central reciprocatory rods or pins 39 and 49 are used to support the thread-case 4I which is like the threadcase 23 in all respects except that it has, in addition to'a hole 42 in its inner face, a coaxial hole 43 in the tip end of the center post or arbor 25.Y The hole 42 is not as deep as the hole 24 in the bobbin-case 23 and the stroke of the rod may be considerably reduced by using a crank- Y, pin like the crank-pin I6 but of reduced eccentricity.

The pin 39 is mounted in an arm 44 which is swiveled on the pin 45 but is normally locked by the spring-pressed plunger 46 to the segmental plate-like'head '41 of a sleeve 48 slidably `supported by the projecting end of a bearing bushing 49 fixed in the bed-lug I. The sleeve 48 has an upstanding arm 50 at itsinner end to which by the spring 53. I

Mounted in the sleeve on the transverse pin l 54 are the rollers 55 which are held separated-by Fig. '7. 'I'he gear ratio of the gears 62, 6I is one from the hole 43 simultaneously with the withdrawal of the pin 4D from the hole 42 for passage of the cast needle-thread-loop, as shown in Fig. 8.

The latch-pin 46 may be withdrawn fron. the upper hole in the segmental plate 41 and the arm 44 swung counter-clockwise, Fig. 9, to a horizontal position, to expose the face of Y the bobbin-case 4I for bobbin removal and replenishment.

Having thus set forth the nature of the invention what I claim herein is:

1. In a sewing machine, a loop-casting hook, a tubular rotary shaft carrying said hook, a nonrotary centrally apertured bobbin-case supported by said hook within its loop-casting field of action, a rod disposed coaxially of and within said tubular shaft, and means to reciprocate said rod endwise to cause it to intermittently enter said bobbin-casebetween loop-casting operations.

2. In a sewing machine, the combination with a rotary loop-taking hook and an apertured stationary bobbin-case having interengaglng circular means to retain the bobbin-case within the field of action of said hook, of 'bobbin-case-supporting means including l'reciprocatory spindle means arranged to enter the aperture in said bobbin-case for the support of the latter for more than one complete rotation of said hook and tov withdraw from said bobbin-case momentarily for passage of the needle-thread-loop.

3. In a sewing machine, a loop-taker, a hollow loop-taker driving shaft, an endwise reciprocatory rod in said shaft, and a non-rotating bobbincase journ-aled in said kloon-taker and intermittently engaged by said rod for support of said Y bobbin-case'.

is fixed a headed pin 5I slidable in a guide-bore 52 of the bed-lug I? and biased in onedirection to four so that the cam-shaft 60 makes one-half 75 4. In a sewing machine, a loop-taker, a hollow loop-taker driving shaft, an endwise-reciprocatory rod in said shaftand a non-rotating bobbin-case journaled in said loop-taker and formed with a central aperture intermittently entered by said rod for support of said bobbin- CaSe.

` 5. In a sewing machine, a bobbin-case having a peripheral bearing and an axial arbor provided with an axial hole, a rotary hook in which the peripheral bearing of said bobbin-'case is. loosely journaled. a tubular hook-driving shaft, and an endwise reciprocatory rod disposed in said shaft and intermittentlyl entering said axial hole to support said bobbin-case and take the weight of the latter oiI oi.' said peripheral bearing.v

6. The combination with a rotary loop-casting hook and a stationary apertured bobbin-case loosely journaled in said hook. of -a tubular hooksupporting drive-shaft terminating at one end adjacent said bobbin-case, a reciprocatory rod extending lengthwise of and within said tubular drive-shaft, and means to reciprocate said rod endwise so as to intermittently project one end thereof beyond the end of said hook-shaft and into the aperture in said bobbin-case tb support the latter, said rod-reciprocating means acting to withdraw said rod from said bobbin-case momentarilyfor passage of the cast needle-loop therebetween.

'1. A sewing machine having a frame including a bed and overhanging bracket-arm, a reciprocatory needle carried by said bracket-arm, a tubular rotary hook shaft journaled in said bed, a rod disposed in and projecting from said hook-shaft, a rotary hook complemental to said needle in the formation o'fjstitches, a bobbin-cas'e journaled in carried by said lower tubular shaft, a non-rotary bobbin-case loosely journaled in said rotary hook and formed with an aperture coaxial with said tubular shaft, and a reciprocatory rod slidable endwise of and within said tubular shaft and aotuated by said crank to intermittently enter said aperture and support said bobbin-case clear of said rotary hook.

9. In a. sewing machine, a loop-casting hook, a bobbin-case, a pair of oppositely disposed pins to support the bobbin-case within the field of action of the hook, means to withdraw said pins from said bobbin-case substantially simultaneously and in time to permit passage of a thread-loop being cast bythe hook about the bobbin-case, and means to hold said bobbin-case in position for re-engagement by said pins.

10. In a sewing machine, a pair of opposed coaxially arranged pins, a bobbin-case supported by said pins, a rotary loop-casting hood having a field embracing said bobbin-case, means to simultaneously and momentarily withdraw said pins from said bobbin-case for the passage of a cast needle-loop, and manually operable means to swing one of said pins to one side for access to said bobbin-case for replenishment of the bobbin-thread supply.

11. In a. sewing machine, the combination with a rotary-` loop-casting hook and a non-rotary apertured bobbn-case confined within the eld of action of said hook, of a crank-driven endwise reciprocatory rod arranged to intermittently enter 'the aperture in said bobbin-case for thesupport of the latter for discontinuous time periods each greater than one-half of the duration of a stitch-forming cycle.

12. The combination with a reciprocatory eyepointed needle and a rotary hook making a plurality of complete rotations for each complete reciprocation of said needle, of a bobbincase confined within the field of action of said hook and. formed with a central aperture, andan endwise reciprocatory rod arranged to intermittently penetrate the aperture in said bobbin-case far enough for the support of the latter during the entire idle rotation of said hook and for the beginning and final portions ofthe loop-casting rotation of the latter.

13. The combination with a reciprocatory eyepointed needle and a rotary hook making a plurality of complete rotations for each complete reciprocation of said needle, of a bobbln-case confined within the field of action of said hook and formed with a central aperture, and a crankdriven endwise reciprocatory rod arranged to intermittently penetrate the aperture in said bobbin-case far enough for the support of the latter during the entire idle rotation of said hook and for the beginning and final portions of the loopcasting rotation of the latter.

14. In a sewing machine, a rotary loop-casting hook formed with a raceway, hook driving means, a non-rotary axially apertured bobbin-case confined by said raceway within the loop-casting field of action of said hook, and an endwise reciprocatory rod arranged on the same side-of the hook as the hook-driving means to enter the axial aperture in said bobbin-case and relieve the bobbin-case'and hook of their tendency to overheat because of friction at said raceway.

JOHN D. KARLE 

